WASHINGTON -- The Supreme Court on Monday rejected Sen. Bob Menendez's request that it take up his federal corruption case, dealing a blow to the New Jersey Democrat's hope of having key evidence and charges dismissed before his trial begins.

The decision was announced Monday morning without comment from the court. It clears the way for Menendez's trial to move forward. It is scheduled to begin Sept. 6.

"Sen. Menendez remains confident that he will be vindicated when all the facts are heard at trial," his lawyer Abbe Lowell said in a statement.

By declining to hear the case, the high court let stand rulings that went against Menendez, and leaves in place evidence prosecutors have used to allege that the senator wielded his power to improperly aid a major donor.

"If he [had] prevailed on this, he could potentially have obtained dismissal of the charges," said Andrew Levchuk, a former prosecutor in the Justice Department's public integrity unit. "The guts of the indictment" would have been inadmissible.

"Now," Levchuk said, "the court has said a jury can hear this evidence."

Menendez had sought the high court review in his fight against charges centering on his relationship with Florida ophthalmologist Salomon Melgen, a wealthy friend and contributor.

Menendez was indicted in April 2015, accused of accepting nearly $1 million in campaign donations and gifts -- including numerous flights on Melgen's private plane and stays at luxurious vacation accommodations in the Dominican Republic and Paris -- in exchange for using his office to press for government action that would help Melgen's business interests.

On one issue, Menendez advocated for policies that would have aided Melgen in a $9 million billing dispute with the government. (Melgen is on trial in a separate Medicare fraud case in Florida.)

"In some ways, the appeal to the Supreme Court was the last hope that they had in trying to knock out part or all of the indictment, based upon a legal challenge," said Lee Vartan, a former prosecutor in the U.S. Attorney's Office for New Jersey. But he argued that Menendez may still have a strong defense at trial. "At the end of the day, the government I think is going to have a difficult time showing there was an explicit agreement between Menendez and Melgen," he said.

Menendez's trial now appears set to begin in the midst of New Jersey's gubernatorial and legislative elections, and a little more than a year before the senator is due to be on the ballot.

At stake politically is a normally safe Democratic seat at a time when the Senate is the party's primary bulwark against the Trump administration and GOP-led Congress. If Menendez is forced out, Gov. Christie could appoint a replacement -- presumably a Republican.

For now, New Jersey Democratic insiders are focused on winning back the governor's office and are not pressuring Menendez to step aside, four party operatives said in interviews. They described little fear of wider fallout.

Instead, the party seems to be hoping the court system effectively decides Menendez's political future. If his trial begins as scheduled, the case is likely to conclude well before next year's election season. A conviction or plea deal would set up a race to replace Menendez without Democrats having to push him out.

If he is cleared, Menendez has signaled he intends to run again -- though even without a conviction, he might carry heavy political baggage.

"He's not up until 2018, and this is going to be resolved this year," said Mike Soliman, a Menendez adviser and one of the few Democrats willing to discuss the senator's political future on the record. "Politically, nothing has really changed from yesterday."

Soliman said Menendez "absolutely" intends to run for a third term, so much so that he held two fundraisers Sunday and a third Monday morning.

In addition, South Jersey political power broker George E. Norcross III and his brother Rep. Donald Norcross (D., N.J.) are headlining a fundraiser for Menendez in May, despite rumors that the congressman would likely run for the Senate if Menendez is forced out.

Menendez had $1.6 million in his campaign fund as of Dec. 31, and a recent Quinnipiac University poll found he had a 51 percent public approval rating, his best since 2012.

But the trial could change the picture, several operatives said.

If it brings out damaging revelations that become talking points during this fall's elections, Democrats on the ballot might be pushed to distance themselves from Menendez, diminishing his political support.

"Bob Menendez is out of legal options and must now answer for these incredibly serious allegations of corruption," said Bob Salera, a spokesman for Republicans' Senate campaign arm.

Menendez and Melgen have said that the donations and gifts were between friends and that the senator's work was simply constituent aid and proper Senate oversight protected by the Constitution's "speech and debate" clause. The clause, intended as a safeguard against executive branch intimidation, shields lawmakers from prosecution for doing their jobs.

The U.S. Court of Appeals for the Third Circuit, however, twice rejected Menendez's arguments last year that his actions in this case were protected. The Supreme Court declined to review that decision. In order to take up the case, four of the eight sitting justices would have had to vote to hear it. The court does not typically release details about those votes or decisions.

Lowell's statement called the decision "disappointing."

"While the senator always understood it is rare that the Supreme Court hears any case before trial, given the gravity of the constitutional issues raised, he believed it was important to try," Lowell said.

Federal prosecutors have argued that Menendez's reading of the law would make senators into "super citizens" shielded from punishment for corruption. A similar battle over the speech and debate clause played out in the trial of former U.S. Rep. Chaka Fattah of Philadelphia, who was convicted on corruption charges last year.

The Supreme Court gave one public official a reprieve last year when it threw out a corruption conviction against former Virginia Gov. Bob McDonnell. While Menendez's team briefly cited that case in its filing to the high court, that decision is more likely to have an impact if Menendez's case goes to a jury, said Levchuk. It created a higher burden for proving a quid pro quo, he said.

A Justice Department spokesman declined to comment on the Supreme Court's decision.